The present invention relates to a blind plug for closing an opening; more particularly, to a plug for sealingly closing an end of a cylindrical bore without use of threaded means; and most particularly, to a formed plastic plug which may be sealingly inserted into a bore without use of tools, which cannot be forced out by differential pressure across the plug, and which can be removed without impairing the sealing properties of the plug, such that the plug can be reused.
Plugs for sealingly closing openings such as bores are well known. A common configuration of a sealing plug has a threaded shank formatably engaging with threads in the bore to draw the plug into the bore, and a cap at the end of the shank having a greater diameter than the bore for forming a seal against a surface surrounding the bore when urged against this surface by action of the threads.
Such a plug has at least three disadvantages. First, both the plug and the bore must be threaded, which can add to the difficulty and cost of manufacture. Second, the plug typically requires a tool, for example, a screwdriver or Allen wrench, for both insertion and removal. Third, a threaded seal is vulnerable to becoming unthreaded and thus developing a leak, particularly when used axially on an object which is subject to sudden, repeated, and extreme changes in rate of rotation about its axis, for example, an automotive cam shaft phaser such as is disclosed in U.S. Pat. No. 5,540,197 issued Jul. 30, 1996 to Golovatai-Schmidt et al., the relevant disclosure of which is hereby incorporated by reference.
Plugs for smooth bores are also known. Typically, such a plug has a close fitting shank which occupies the bore in an almost interference fit, an oversized cap for limiting ingress into the bore, and a flexible latching means at the inner end for engaging the inner end of the bore. There are two serious shortcomings of this type of plug. First, the seal is not a true bore seal but also depends typically upon having the latching means urge the cap against the surface surrounding the outer end of the bore with a force sufficient to prevent leakage between the cap and the surface. Thus internal pressure under the plug must raise the plug only a very small distance to create a leak. Second, removal of the plug requires inserting a screwdriver or other prying tool under the edge of the cap. This action can readily damage the plug such that it cannot be reused.
It is a principal object of the invention to provide an improved plug which may be inserted manually into a bore to form a seal with the wall of the bore.
It is a further object of the invention to provide an improved plug which may be readily removed from a bore without requiring special tools and without impairing the future sealing capability of the plug.
It is a still further object of the invention to provide an improved plug which may be formed inexpensively, as by molding from a plastic polymer. It is a still further object of the invention to provide an improved plug which cannot be loosened by axial rotation.
It is a still further object of the invention to provide an improved plug which cannot be forced out of a bore by pressure differential across the plug.
Briefly described, an improved releasable, reusable, self-sealing plug for sealing a bore in accordance with the invention has a cylindrical body, formed on its outer surface to retain sealing means, such as an O-ring, for sealing against the wall of the bore. An oversize annular cap at the outer end limits ingress of the plug into a bore, and a pair of opposed, flexible flanges at the inner end are compressed during insertion and spring out at completion of insertion to grip the inner entrance to the bore, thus holding the plug in the bore. The plug cannot be driven out by pressure in the bore, but is easily removed by recompression of the flanges and withdrawal by, for example, needle-nose pliers. Such recompression and withdrawal does not impair the sealing capability of the plug, so that the plug may be reused repeatedly if so desired. The plug may be easily and inexpensively formed by injection molding of a suitable polymer.